[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH v5 02/21] Document ioemu Linux stubdomain protocol
From: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx> Add documentation for upcoming Linux stubdomain for qemu-upstream. Signed-off-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx> Signed-off-by: Jason Andryuk <jandryuk@xxxxxxxxx> --- docs/misc/stubdom.txt | 50 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 50 insertions(+) diff --git a/docs/misc/stubdom.txt b/docs/misc/stubdom.txt index 64c77d9b64..bb5e87dfb9 100644 --- a/docs/misc/stubdom.txt +++ b/docs/misc/stubdom.txt @@ -75,6 +75,56 @@ Defined commands: - "running" - success +Toolstack to Linux ioemu stubdomain protocol +-------------------------------------------- + +This section describe communication protocol between toolstack and +qemu-upstream running in Linux stubdomain. The protocol include +expectations of both stubdomain, and qemu. + +Setup (done by toolstack, expected by stubdomain): + - Block devices for target domain are connected as PV disks to stubdomain, + according to configuration order, starting with xvda + - Network devices for target domain are connected as PV nics to stubdomain, + according to configuration order, starting with 0 + - [not implemented] if graphics output is expected, VFB and VKB devices are set for stubdomain + (its backend is responsible for exposing them using appropriate protocol + like VNC or Spice) + - other target domain's devices are not connected at this point to stubdomain + (may be hot-plugged later) + - QEMU command line is stored in + /vm/<target-uuid>/image/dmargs xenstore dir, each argument as separate key + in form /vm/<target-uuid>/image/dmargs/NNN, where NNN is 0-padded argument + number + - target domain id is stored in /local/domain/<stubdom-id>/target xenstore path +?? - bios type is stored in /local/domain/<target-id>/hvmloader/bios + - stubdomain's console 0 is connected to qemu log file + - stubdomain's console 1 is connected to qemu save file (for saving state) + - stubdomain's console 2 is connected to qemu save file (for restoring state) + - next consoles are connected according to target guest's serial console configuration + +Environment exposed by stubdomain to qemu (needed to construct appropriate qemu command line and later interact with qmp): + - target domain's disks are available as /dev/xvd[a-z] + - console 2 (incoming domain state) is connected with FD 3 + - console 1 (saving domain state) is added over QMP to qemu as "fdset-id 1" (done by stubdomain, toolstack doesn't need to care about it) + - nics are connected to relevant stubdomain PV vifs when available (qemu -netdev should specify ifname= explicitly) + +Startup: +1. toolstack starts PV stubdomain with stubdom-linux-kernel kernel and stubdom-linux-initrd initrd +2. stubdomain initialize relevant devices +3. stubdomain starts qemu with requested command line, plus few stubdomain specific ones - including local qmp access options +4. stubdomain starts vchan server on /local/domain/<stubdom-id>/device-model/<target-id>/qmp-vchan, exposing qmp socket to the toolstack +5. qemu signal readiness by writing "running" to /local/domain/<stubdom-id>/device-model/<target-id>/state xenstore path +6. now device model is considered running + +QEMU can be controlled using QMP over vchan at /local/domain/<stubdom-id>/device-model/<target-id>/qmp-vchan. Only one simultaneous connection is supported and toolstack needs to ensure that. + +Limitations: + - PCI passthrough require permissive mode + - only one nic is supported + - at most 26 emulated disks are supported (more are still available as PV disks) + - graphics output (VNC/SDL/Spice) not supported + PV-GRUB ======= -- 2.20.1
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